Baking is one of the oldest activities in the field of artisan food preparation. Flat bread was produced from ground grain and water as early as 8,000 years ago. By comparison, vacuum technology is relatively new. Technically speaking, a vacuum was first generated in the 17th century, and is today an inherent and essential part of industrial practice. Our highly technical world now needs vacuum more than ever. Here are 6 ways vacuum improves bread production, and the vacuum pumps that make it profitable.
1. Crispy crust, loose crumb
Vacuum technology has brought innovations to the industrial baking trade. The cooling of baked goods is being revolutionized. In comparison to conventionally cooled baked goods, the advantage of vacuum-cooled bread is clear from the very first touch. The crust is crispy and the crumb is loose. Through the extension of the so-called crusting process, the volume consistency of the baked goods also increased; resulting in a crust that is stable for longer and brittle, yet soft. This is of great advantage, as many baked goods tend to lose their form in environments with higher air humidity. A stable volume is not only a win in terms of quality for the customer; it also offers an advantage over the competition in terms of appearance when the baked goods on display not only smell delicious but also look attractive and entice shoppers to make a purchase.
Fig. 1: Vacuum-conditioned bakery products convince through a uniform crumb as well as a larger and dimensionally stable volume
2. Fewer bacteria in the vacuum
Alongside the advantages to the purchaser that are evident upon first glance, there are a few other important aspects to be considered. By accelerating the process, the time window for the development of bacteria is shortened. In vacuum cooling, the critical temperature range for the growth of mold spores (from 60°C to 30°C) is cut to 2 - 3 minutes, rather than two hours, as was previously the case. Cooling in an enclosed chamber simultaneously serves as a sluice between production and packaging. It also significantly reduces the risk of airborne bacterial attack and the resulting spore formation. This means that there is no need for a costly sterilization process following packaging in order to resist the formation of spores. Only pure air and protective gas could further extend the shelf life.
Related: Safety regulations in food production are on the increase, and the food industry is under pressure to evolve if it wants to stay profitable beyond 2020. Download a copy of our eBook on The Future of Food, and find out how vacuum helps industrial food production become more efficient and profitable.
There are other benefits of vacuum cooling in baking. Compared to conventional air cooling, the compact dimensions of a vacuum cooling system frees up significant space, saving up to one tenth of the floor space previously used. A simple conditioning chamber has a chamber size of around 120 x 100 cm and is approximately 2 meters tall. Vacuum pumps or switch cabinets are functionally integrated into the system directly alongside the chamber. The recovered space can then be used for additional production capacities within the company. Breads of various types and sizes can be cooled to 30°C within just 5 - 10 minutes.
Thus, the bakery not only benefits from an improvement in quality, but also from increased productivity. The new cooling technology drastically reduces the original cooling phase. Meanwhile, the baked goods are optimally conditioned for the subsequent processing steps of slicing and packaging. The systems commonly used today are designed for a rack trolley with a sheet size of 60 x 100 cm. Depending on the product, up to twelve batches, or 400 - 500 kg of baked dough, can be conditioned each hour. By comparison, cooling in ambient air can last several hours. Vacuum-cooled baked goods are quicker and easier to prepare for the subsequent processing chain.
4. Vacuum conditioning improves the quality of baked goods
One of the main technical challenges in the vacuum conditioning of baked goods is that the system manufacturers must cater to many different bread types, with varied recipes and a wide range of ingredients. Just think of the breakfast breads found in European baking culture and the differences between various baked goods becomes evident. Croissants, baguettes, roggenbrot or hefezopf with raisins – the unique qualities of each recipe are reflected in the equipment and control system used. The equipment manufacturer must program the corresponding cooling sequences for the respective baked goods into the equipment control system. This requires specific baking expertise and years of experience. Here, vacuum technology has almost as much influence over the quality of the goods as the baking recipe itself.
The vacuum conditioning of baked goods is also ideally suited for the bakery or point of sale concept that is common today. Baking generally takes place at a decentralized location outside of the town or city. The baked goods are then delivered to points of sale in the city or in shopping centers. The customer's expectation of being able to buy fresh and warm bread rolls at any time of day can be optimally fulfilled with the help of vacuum conditioning.
Related: Vacuum technology is also used to freeze dry food and preserve it, while retaining its look and feel and maintaining its nutritional value. Click the button below and find out how vacuum has improved food preservation on our resource page.
The key here is a process called pre-baking. Pre-baked goods are conditioned using vacuum and can be delivered to the points of sale without intensive cooling, where they can then be stored for up to four days. Thus, deliveries are often made to several branches of a business, spanning large distances. As a result of vacuum conditioning, the products are delivered to the branches undamaged, without packaging, even in the most varied of weather conditions. The baking of the vacuum-conditioned bread is then simply finished at the bakery, with cooking times reduced on account of the goods being pre-baked. Energy consumption can be significantly reduced by using this interrupted baking method. Logistic costs are also reduced because the deep-cooling logistics and storage previously required within the baking factory and the retail branches is eliminated.
The shortened baking process is also much more convenient for staff, as exhaust air and heat generation are significantly reduced. The customer can enjoy fresh, warm and perfectly shaped bread around the clock - instant indulgence, in keeping with the modern lifestyle.
Fig. 2: Batch unit for vacuum conditioning, oven racks enable quick loading
6. Cooling times reduced; condensation prevented
The second major technical challenge lies in the technical design of the vacuum cooling and conditioning system. Here the principle of vacuum cooling is used. At atmospheric pressure, water boils at 100°C. If the atmospheric pressure is reduced, the boiling point also falls. If the pressure lies at 42 mbar, water evaporates at just 30°C. The energy required for the water to boil is drawn from the baked product, which is still almost oven warm. Depending on the product, standard cooling times are between 2 and 6 minutes. During this time, the bread cools evenly across the entire product. The uniform extraction of the water content also prevents possible condensation in the bread itself, a process often referred to as gelatinization. This in turn results in an increase in quality for the bread-lover.
The hot or warm steam produced as a result of the process poses a challenge in the technical design of the vacuum cooling and conditioning system. What is more, the steam is not pure but is contaminated with baking ingredients such as flour, yeast, sugar and salt. This is vitally important to consider when selecting the vacuum pump technology. No vacuum pump would withstand contamination with steam and a mushy, sticky-sweet mass in the long-term, and the use of a liquid ring pump should be avoided. In principle these technologies would be ideal, but here the dependency of the final pressure on the water temperature is not conducive to the process. Ultimately, this raises the question whether to use a pump with classic, oil-sealed rotary slide technology or modern, oil-free screw technology. At this point it is difficult to name a preference. In principle, both pumps are suitable, however the design of the vacuum cooling system is decisive in making a choice.
Fig. 3: Two-chamber conditioning units with optimally integrated oil-free vacuum pumps during assembly.
Related: Hygiene and equipment sanitation are top-of-mind for food producers. Vacuum pumps often come with enclosures that ensure they can be thoroughly cleaned, while keeping the pump safe from exposure. Read more in our blog post on how Food Safety Has Always Been Paramount, and how vacuum pump manufacturers like Leybold ensure that incorporating the benefits of vacuum into the production line doesn't compromise health and safety.
The trend points towards dry, screw type technology
Smooth operation depends on the skill of the equipment manufacturer in implementing the correct measures for operation and servicing, in order to protect the chosen pump from the steam and ingredients mixture. If you consider the vacuum cooling systems available on the market, there is, however, a notable trend towards the use of oil-free screw technology. This is without doubt due to the fact that modern screw pumps with frequency converters can be optimally combined and integrated with the equipment control system in a compact manner. With regard to noise emissions, these screw pumps also offer the comfort of low-noise operation. Hygiene regulations in food production also take this factor into account. Many baking companies shun frequent oil changes, which come with associated costs.
Fig. 4: NOVADRY Modern, oil-free, screw-type vacuum pumps are most appropriate for vacuum conditioning bakery products
But this is set to change. Closer consideration of the new baking technology shows that by using vacuum, equipment manufacturers, producers, bakeries and consumers all reap equal benefit. They all profit from an increase in quality and productivity. Plus, the potential is huge for improvement in production times, infrastructure personnel, logistics cost, raw material and energy consumption. The technical and financial prerequisites to market penetration are thus undoubtedly fulfilled.
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Disclaimer: Original Author Klaus Buhlmann, Market Sector Manager, Leybold GmbH